The epididymis is the site, in mammals, where spermatozoa mature (acquire the ability to fertilize) and are stored. In spite of our growing knowledge about what the epididymis does and how it does it, virtually no effort has been invested in determining how this tissue is affected by the process of aging. The aging Brown Norway rat offers the unique opportunity of studying aging of the reproductive system without the complexities consequent to simultaneous pathological changes in other systems, most notably the pituitary and the liver. The long-term objective of this project is to determine how the epididymis changes as animals age. The major goals are to determine 1) how the process of aging affects specific morphological and functional characteristics of the epididymis, and 2) whether the age-associated changes are mediated by endocrine or paracrine mechanisms. To attain the first goal, three complementary approaches will be used. For all three, the epididymides of 3-30 month-old Brown Norway rats will be studied. The first approach is to determine how the major histological features of the tissues are affected by age. The second approach is to use selective biochemical markers of epididymal function to assess which facets of the tissue are affected. Northern and Western blot analyses, enzyme assays and immunocytochemistry will be used to examine changes taking place in 4-ene steroid 5a-reductase, and androgen receptor, epithelial cadherin, immobilia, sulfated glycoprotein-2, acidic epididymal glycoprotein, glutathione S-transferases, and proenkephalin. The third approach is to assess the fertility of the animals as they age and relate it to the changes taking place in the testis and the epididymis. The second major goal of this application will also be attained by doing three types of manipulations designed to isolate the impact of endocrine and paracrine factors on the epididymis. The three manipulations are orchidectomy, efferent duct ligation and steroid treatments designed to alter specific testicular cell type(s). Together, these studies will provide the first detailed studies of the consequences of aging on epididymal structure and function. Whether the effects of aging on this tissue are intrinsic to it or secondary to events taking place in the testis will also be determined.